This application is directed to the use of additive concentrations of neutralized metallic hydrocarbyl sulfonate/dialkyl cyclic (or non-cyclic) phosphite reaction products in premium quality industrial, automotive and marine lubricants which provide a "time-release" dosage of multifunctional friction reducing antiwear properties and thus extend service life.
Lubricants, such as lubricating oils and greases, are subject to oxidative deterioration at elevated temperatures or upon prolonged exposure to the elements. Such deterioration is evidenced, in many instances, by an increase in acidity and in viscosity, and when the deterioration is severe enough, it can cause metal parts to corrode. Additionally, severe oxidation leads to a loss of lubrication properties, and in especially severe cases this may cause complete breakdown of the device being lubricated. Many additives have been tried. However, many of them are only marginally effective except at high concentrations. Improved antioxidants are clearly needed.
Antioxidants or oxidation inhibitors are used to minimize the effects of oil deterioration that occur when hot oil is contacted with air. The degree and rate or oxidation will depend on temperature, air and oil flow rates and, of particular importance, on the presence of metals that may catalytically promote oxidation. Antioxidants generally function by prevention of chain peroxide reaction and/or metal catalyst deactivation. They prevent the formation of acid sludges, darkening of the oil and increases in viscosity due to the formation of polymeric materials.
Water (moisture) is another critical problem. In spite of even extraordinary precautionary efforts water is found as a film or in minute droplets in vessels containing various hydrocarbon distillates. This brings about ideal conditions for corrosion and damage of metal surfaces of the vessels and the materials contained therein. Also in the lubrication of internal combustion engines, for example, quantities of water are often present as a separate phase within the lubricating system. Another serious problem in respect to metallic surfaces in contact with adjacent metallic surfaces is the surface wear caused by the contact of such surfaces. One material capable of simultaneously effectively coping with such problems as these is highly desirable.
Lubricants in service applications often generate acid species or acid-forming species, especially when exposed to high operating temperatures, extended service life and/or contact with atmospheric oxygen during aeration caused by churning or moving elements of the lubricated machine. Acid-forming species can also be formed via hydrolysis or other similar mechanisms.
Metallic aryl sulfonates such as calcium dinonylnaphthalene sulfonates have been widely used in petroleum and synthetic lubricants as rust and corrosion inhibiting additives. Additionally, these and related metallic aryl sulfonates have, on occasion, provided good detergency and demulsibility properties in a variety of lubricant formulations.
It has now been found that if metallic aryl sulfonates are used as additives in systems as described above, neutralization or acidification to form sulfonic acids can occur. If both metallic aryl sulfonates and di- or trialkyl diol or alkoxylated amine phosphites are used together in a lubricant, or alternatively pre-reacted, these sulfonic acids and phosphites can react to form sulfonate esters and lower phosphites having one less alkyl substitutent group. This mechanism can thus provide a "time-release" dosage of friction reducing, corrosion inhibiting or antiwear additives during the latter stages of lubricant service life when performance improvement is most needed. This phenomena can also be effectively used to neutralize potentially harmful acid substances as soon as they are generated. These remarkable benefits can be provided for a variety of synthetic and mineral oil based lubricants.
It is an object of this invention to provide both (a) a unique lubricant additive composition made by the reaction of at least partially neutralized or acidified sulfonates with alkanediol or alkoxylated amine phosphites, and (b) a method of providing for "time release" friction reducing, corrosion inhibiting, and/or antiwear properties via appropriate blending of sulfonate and phosphite components, allowing for the acidification or neutralization of the sulfonate in situ, in service and then the co-reaction of the acidified sulfonate and diol or alkoxylated amine phosphite while in use.
To the best of our knowledge the compositions in accordance with the invention have not been previously used as multifunctional additives in lubricating oils or greases or other solids lubricants. The use of reaction products of acidified sulfonates and cyclic phosphites or alkoxylated amine phosphites as multifunctional additives has not been reported in the literature and are believed to be novel. The composition of matter, the lubricant compositions containing such additives, and the use of such reaction products and lubricants to improve the performance properties are also unique.
The use of sulfonates and diol-derived or alkoxylated amine phosphites as "time-release" multifunctional additives for lubricants which function via at least partial neutralization or acidification followed by phosphite esterification is also believed to be both unique and novel.